Hand held breath analyzing devices are in common use by police departments throughout the world. Such a device, with a now conventional fuel cell and pump chamber and circuit is described in Wolf U.S. Pat. No. 4,487,055, and a more detailed circuit arrangement is described in Wolf U.S. Pat. No. 4,770,026. These are merely illustrative, but their teachings are useful in understanding the present invention.
Police officers in the field are understandably somewhat reluctant to handle a mouthpiece dripping with the saliva of a suspected drunk. The breath of the subject is also likely to be loaded with moisture and contaminants that, with continued use of the device, tend to affect the operation of a thermistor in the breath path. Under field conditions, when it is likely to be dark and the weather conditions poor, it is desirable to have the operation of the device automated as much as possible, and to simplify the operation of the device from the patrolman's point of view, by minimizing the numbers of switches to operate and steps to remember. It is also desirable to insure that all the conditions precedent to the proper operation of the device be met before a sample is attempted to be taken. It is also desirable to prolong the useful life of the various elements, including the fuel cell, and to make the device as simple, rugged, and dependable as possible.